Are the new 84-tooth gears more flexible than you might expect?

My kids were excited when they got their hands on some of the new high strength components. However, when they started fiddling with the new 84-tooth gears, they pointed out to me how flexible they are. I admit they seem a little more bendable than I would expect. A simple piece of plate mounted to the sides would certainly help them, but one of the kids seems to think they are made of a plastic that’s softer than the other, older high strength gears. Has anyone else noticed any significant difference with these new gears? I’m just curious.

Thats interesting when my season starts I will check that out

The old gears are made of Delrin and the new 84-tooth is made of “PAG Unreinforced Nylon.”

According to the internet, a highly reputable source /s, nylon is typically not as strong as delrin. Perhaps a materials engineer aficionado could give a better comparison.

You should ask in the official answers forum. VEX is good about getting back to this kind of question.

As far as the materials go, Nylon and Delrin have similar stiffness (elastic modulus), so I don’t think it’s entirely the material. The larger gears are, well, larger, so they will naturally bend more than their smaller counterparts. If the gears have the same wall thickness, the 84-tooth ones should deflect about 2x as much at the edges than their 60-tooth counterparts.

The material was changed from POM (AKA acetal or Delrin) to PA6 (Nylon) to increase the strength of the gear. Switching to PA6 increased the yield strength of the gear material by around 50%. In the past POM was chosen for most VEX motion components because it has a very low coefficient of friction and can even be self-lubricating in certain circumstances. Due to the higher torques that the 84t gear will see when used on robots, the VEX engineering staff elected to use Nylon, which also has a low coefficient of friction, for the gear.

The gear may seem less stiff than the existing high strength gears, but this is due to a difference in geometry, not material strength - the large size of the 84t gear makes it naturally less rigid than the smaller high strength gears. However due to the increase in material strength, it is capable of carrying more torque without failing.

Let me know if there are any further questions,


Have you done any tests with regard to teeth chipping off when the 84 tooth gear is compared to the 36 or 60?

We haven’t had any chipping of any teeth in our early prototype testing. We’ve lifted many different loads.

Great jobs VEX development crew!!:D:D

I believe the new material, since it is less hard, will chip less, and instead allow small amounts of flexing within the range of elastic deformation; in other words not causing permanent damage, which will cut down on chipping and breaking of gears, although if the material is less hard it may strip out quicker especially if it is meshing with a metal gear, as the metal gear has much less of a deformation range as it is much harder.